In divided-chamber gas engines, it is important to keep a normal combustion state of the auxiliary chamber in order to improve the combustion efficiency of the main combustion chamber to realize energy saving and reduce imperfectly combusted components, including uncombusted hydrocarbon components in exhaust gas, thereby realizing clean conditions. For keeping a normal combustion state of the auxiliary chamber, it is effective to supply a suitable amount of gaseous fuel to the auxiliary chamber in a timely manner. In this respect, in conventional divided-chamber gas engines, an auxiliary chamber fuel supply valve for supplying a gaseous fuel to the auxiliary chamber is configured as a solenoid valve, and opening and closing of the auxiliary chamber fuel supply valve are controlled in accordance with engine operating conditions, such as an engine speed. For example, the valve-opening timing or valve-closing timing of the auxiliary chamber fuel supply valve is set to be a suitable timing for the start of fuel supply or the end of fuel supply to the auxiliary chamber.
In such a divided-chamber gas engine, a non-return valve is interposed between the auxiliary chamber fuel supply valve and the auxiliary chamber. The non-return valve allows a flow from the auxiliary chamber fuel supply valve to the auxiliary chamber, but blocks a reverse flow from the auxiliary chamber, thereby allowing fuel supply to the auxiliary chamber while protecting the auxiliary chamber fuel supply valve from a flame and combusted gas generated in the auxiliary chamber. Conventionally, various operating manners of non-return valves for use in divided-chamber gas engines have been proposed, for example, spring-operated valves, magnet-operated valves, and cam-driven valves.
Patent Literature 1 discloses a spring-operated non-return valve. The valving element of the non-return valve is urged by elastic force of a spring, and thereby the non-return valve is normally in a closed state. When a solenoid valve (an auxiliary chamber fuel supply valve) is opened, the pressure of a gaseous fuel that has passed through the solenoid valve causes the valving element of the non-return valve to move against the elastic force. As a result, the non-return valve opens. Consequently, the gaseous fuel passes through the non-return valve, and is supplied into the auxiliary chamber.